ABSTRACT
Rainfall and runoff processes can be numerically simulated using computer models. Applying hydrodynamic laws to the flow movement, a rainfall time-distribution is converted into a runoff hydrograph by various numerical schemes. Although the rainfall/runoff process is highly nonlinear, several linear approaches such as the unit hydrograph procedure and the Rational method are still recommended. The major assumption of a unit hydrograph approach is the linear relationship between runoff rate and excess rainfall depth. Prediction techniques for stormwater hydrographs are generally classified into two major categories: (1) the unit hydrograph (UG) method, and (2) the kinematic wave (KW) approach. As common practice in the unit hydrograph method, the length to the watershed’s centroid represents the watershed shape factor (Snyder 1938). The kinematic wave theory for overland flows is a simplified approach of dynamic waves stated in the Saint-Venant equations. Solutions of KW overland flows have been developed for rectangular planes. In this chapter, the dimensionless kinematic wave hydrograph is introduced is and compared with the SCS unit hydrograph (SCSUH) and Colorado unit hydrograph procedure (CUHP). The analytical solution for the KW method is applicable to urban catchments up to 150 to 200 acres.
